US2425634A - Control method and arrangement for a two temperature refrigerator using a capillary expansion device - Google Patents

Description

Aug. 12, 1947. MUFFLY 2,425,634

CONTROL METHOD AND ANGEMENT FOR A TWO TEMPERATURE REFRIGERATOR USING A CAPILLARY EXPAN 0N DEVICE Original Filed July 18, 19 2 Sheets-Sheet l INVENTOR i /r17 fizz/fly.

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2,425,634 MPERATURE DEVICE 940 2 Sheets-Sheet 2 g- 1947- G. MUFFLY CONTROL METHOD AND ARRANGEMENT FOR A TWO TE REFRIGERATOR USING A CAPILLARY EXPANSION Original Filed July 8. 1

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- INVENTOR l 6/2 Muff/ y.

W W know E? A 'fienteJ A l 1947 CONTROL a FOR A. TWO

TOR USING A DEVICE METHOD AND ARRANGEMENT TEMPERATURE REFRIGERA- CAPILLARY EIHANSION aim Mufiy, Springfield, Ohio Bontinuation or July 18, 1940. This application I Serial No. 477,519

application Serial No.

346,085, March 1, 1943,

17 Claims. (01. 62-3) control devices for erant to each of two or more evaporators.

The present application is a continuation of my application for Letters Patent of the United States for improvements in Refrigerating mechanism, filed July 18, 1940; and serially 346,085.

An object of this invention is to provide a vapor-lock type of expansion device having means for immediately cooling upon starting of the system to avoid an excessive degree of vaporlock efiect at the start of an operating cycle of the system.

Another object is to adapt a single expansion device for use in regulating the flow f refrigerant to a pair of evaporators operated at difierent evaporating pressures.

An additional object is to provide a capillary expansion device arranged to serve two evaporators and to trap a charge of liquid refrigerant 1 in each of a pair of evaporators when they are both idle and in the idle one when only one is idle.

Another object is to provide a. capillary expansion device formed by a spirally corrugated shell fitted within a bore and around a core.

A further object is to provide a capillary expansion device that is readily cleanable and associated with a removable filter.

An additional object is to provide a valve mechanism for selectively refrigerating a pair of evaporators and to provide said device with means operable externally for putting the entire low side of the system in communication with the suction side of the compressor for the purpose of evacuating the system.

Another object is to provide an improved form of heat exchange for cooling the liquid refrigerant prior to its passage into the fiow regulating device.

Still another object is to provide a pair of co-acting valves, one controlling the inlet of liquid refrigerant to one evaporator and the other controlling the outlet of the other evaporator, together with a. mechanical connection between said valves arranged to minimize fluid leakage numbered between the separate passages leading to the re spective valves.

when the term vapor-10c appears in this specification or in a claim it refers to that general class of refrigerant flow controlling devices commonly referred to as capillary tubes,v as restrictors, as orifices, as fixed passages of restricted diameter," etc., the term vapor-lock being used because it defines more exactly how such devices operate to substantially prevent flow of vapor therethrough during operation of "the compressor, to be affected by temperature changes and yet remain open to allow a relatively slow flow of vapor sufficient to substantially equalize pressures during idle periods.

In the accompanying drawings, where similar reference numbers represent similar parts:

Fig. 1 is a vertical sectional view through a valve mechanism and capillary control device adapted for use in a two-temperature refrigerating system;

Fig. 2 is a plan view of the valve and refrigerant control device seen in Fig. 1,;

Fig. 3 is an enlarged detail sectional view showing a portion of the capillary deviceof Fig. 1;

Fig. 4 is a more or less diagrammatic view of a complete refrigerating system including the apparatus seen in the preceding views, showing its relation to the evaporators and to the switch. for controlling and the starting and stopping of the system;

Fig. 5 is an alternative construction of the filter and capillary expander parts of Fig. 1;

Figs. 6 to 13, inclusive, are details of the various cllsscs used in Fig. 5 to make up the capillary stack Fig. 14 shows the heavier disc H4 used in Fig. 5 below the capillary discs;

Fig. 15 is a sectional view of Fig. 11, showing how the various discs are locked together;

Fig. 16 is a sectional view or an assembly including a filter and a set of capillary discs, both being retained by their outside diameters instead of by a central screw as seen in Fig. 5;

Fig. 1'? is a sectional view similar to Fig. 16 but showing a filter on each side of the stack of capillary discs to providefor the flow of refrigerant in either direction;

Fig. 18 is a sectional view illustrating a m'odified form of housing for the filter and capillary discs;

Fig. 19 shows the special disc [48 which is used 4 in Fig. 18; and, r

Fig. 20 is a fractional sectional view showing a, slight modification of Fig. 1 to illustrate a variation of the method for passing refrigerant to the warmer evaporator. v

Referring to Fig. 1 we see the valve parts in the positions they assume at the end of an operating cycle of the system, with valve 28 open,

to enter the chamber 82' and the bellows 44. This pressure will expand the bellows 44,' carrying its head 46 and the push rod 81 upwardly to the point of tilting'rocker 88 (Fig. 4) on its pivot 88, causing the switch I23 to close the circuit I26- |28I24 of motor 8 and start the compressor 6. The compressor now draws refrigerant vapor from the warmer evaporator I2 through tube 14 and passages I8 and 88, upwardly past the flutes 31 of valve stem 35 (Fig. 1),' past valve 48, through chamber 82, passage 84, union 85 and tube 86 to the suction side of compressor 6.

As this vapor is compressed and delivered to the condenser I8 the pressure rises to the condensing point due to the fact that vapor cannot pass the vapor lock device I8-I8-28 of Fig. l

V as rapidly as it is pumped by the compressor 6. As the refrigerant liquefies in the condenserl8 and passes through the tube II, the union |8 4 as this gradual closing of the valve 48 produces an appreciable pressure-drop which will result in therapid closing of the valve 48 as described in connection with valve 88 of my copendingapplication Serial No. 331,683, filed April23, 1940.v

In addition to the operation described in this earlier application I show the push rod 33, the valve 26 and its spring 21. The length of'push rod 83 is such that the final rapid movement of the valve 48 in closing causes a slight downward movement of valve 26 against spring 21. -This slight opening of valve 26 is suflicient to pass and the filter I1 it is further passed between the spirally corrugated shell 28 and the wall of the chamber I8 to the upper extremity of the shell 28, at which point it is free to enter the spiral passage between the part. 28 and the core III.

The liquid thus returns to near the bottom of the parts I8 and 28 and passes from the spiral passage or from the annular passage 24 through one of the drilled holes 2| to the-bore within the part I8. Due to the larger cross- .ction of this bore the liquid now starts evaporating,.but

the bulk of; the liquid, along with what vapor has already been formed, flows upwardly through the valve seat 68, lifting the check valve 62 to flow through the passages 66 and 68 and through tube I2 to the higher temperature box evaporator I2.

It will be understood that liquid-refrigerant cannot flow through the passage 22 andpast the valve 26, since this valve was closed by the spring 21 at the time the valve 48 was lifted from its' fseat. It should also be noted that we are now operating on the higher pressure one of the two evaporators, hence none of the vapor from the 'freezer or lower temperature evaporator I4 can lift the valve 62. The freezer is, therefore, isolated by the valves 26 and 62' so that the system operates for the'time being as if there were .only the one evaporator I2. port of the 'valve 26 and the strength of the spring 21 are so proportioned that the valve 26.

The area of the will not be opened by liquid pressure in the liquid refrigerant as rapidly as it comes through the hole 2|, hence there will be no more flow of liquid refrigerant to the higher pressure box evaporator past the valve 82.

ate the bore 84 and begin pulling lower pressure refrigerant from the freezer evaporator I4 through the tube I88 and'the passage I82 of union IIII, lifting the check valve 62' in bore I83, while liquid flows through union 28 and v compressor will continue to operate, pulling vapor from the freezer until the pressure within the bellows falls further, allowingthe head 46 and the push rod 81 to fall under the action of the spring 88 until the switch I28 returns to its 'open position as seen in Fig. 4, stopping the operation of the system.- with all parts returned to their relative positions as seen in Fig. 1

To facilitate evacuating and charging of the system, means is provided for locking the bel-' -lows head 46 in a position nearer the lower extremity of its travel or in a position nearer the upper extremity of its travel. The stamping 8| is so formed as to provide a tubular protection around the bellows; a spacer between the valve assembly 4 and the switch assembly 3, a support I for mounting the entire assembly 2, several inwardly turned projections forming a stop. at the extreme upward movement ofthe bellows head 46, and an opening 82 which serves as a fulcrum for the lever 83. This lever is forked to straddle the push rod 81 with ample clearance and is pivoted by a pair of rivets 84 to an upwardly extendinglug on each side of the center of head 46. In order to retain the lever 88 in.

' the position shown, the operator can with his chamber 23 during the time that the warmer evaporator is in operation. The area of the port closed by the valve 26 is for this reason made quite small. A very small opening will suffice to pass liquid at this point.

As the evaporator I2, located in the main food' compartment of the refrigerator I'3'in Fig. 4, is cooled the pressure within the suction tube I4 falls, thus reducing the pressure within the bellows 44- so that the bellows head 4'6 is pushed downwardly by push rod 8'! under the .action of spring 88, which is" seen in Fig. 4. This brings thumb push the stirrup as to the right so that it is hooked over the projection 86 of the part 8|. Conversely the lever 83 may be pushed downwardly to lift the bellows head 46 to a point near the upper limit of its travel and it maybe locked in this position by pushing the stirrup 85 under the extension 86. In this position the compressorwill evacuate both evaporators and all of the low-side connections.

In the normal automatic operation of the system the parts 83, 84, 85 and 86 have. no function. They are provided for convenience in servicing and to allow manually setting 'of the control for compress the bellows to the cut-out point of switch assembly 3, then hooking the stirrup over the extension 86 and letting the bellows return to the pointat which this holds it. If the lever 83 is lifted while the system is in operation only enough the valve 48 nearer to its seat, until such a time 15 to allow the stirrup 85 to swing over the projection The closing of .valve 48 allows the compressor to quickly evacu- 96 we will have forced the valve 40 to close and the valve 26 to open thus artificially starting operation on the freezer. An additional lug such as 95 or a series of notches in the part 95 may be provided for locking the bellows head in any desired position.

The fo zlred end of the lever 93 and its relation to the bosses on the bellows head "may be 'seen in Fig. 2. The handle end of lever 93 is so designed that it may be inserted through the hole 92 in assembly and the retainer strap 95 is then assembled to the lever 93 by means of a-cotterpin so that it is readily removable for disassembly.

In order to understand how it is possible to operate each of the evaporators at its desired pressure, say ten pounds in the freezer and thirty pounds in the box evaporator with F l2 as the refrigerant, it is necessary to understand more clearl than has been explainedin any publication just how a capillary expansion device operates in a refrigerating system.

The elongated spiral passage formed between the part 20 and the bore [8, together with the continuation of this passage formed between the parts l9 and 20, operates in the same manner as a capillary tube, but the operation of capillary tubes has heretofore been commonly misunderstood. The fact is that a capillary passage, no matter how formed, will pass a much greater weight of liquid per hour than it will pass of the vapor formed from the same liquid. This comparison being made for a given pressure difference between the ends of the passage. The principle which makes a capillary tube or passage effective to pass liquid and not topass vapor is that when there is no liquid ahead of the capillary passage the rate of vapor flow through the capillary passage is such a small percentage of the capacity of the compressor in pounds of refrigerant per hour that there will be a very rapid increase of pressure in the condenser and this will cause the condensation of refrigerant to supply liquid to the capillary passage again.

The rate of refrigerant flow in liquid form may be greater than the rate of vapor flow through a given capillary passage in the ratio of ,2 or more to 1. This means that a capillary expansion device of a given cross-section, length and form will be usable under considerable variation of the conditionswhich affect the number of pounds of refrigerant per hour required to pass through the capillary device.

Since an expansion device of the capillary type acts to pass liquid refrigerant as rapidly as it is condensed, very much like a high side float valve. it will be understood that the capillary device has of itself no action of a pressure regulating nature. It is not the capillary expansion device which-determines the pressure-temperature condition in the evaporator which it serves. The pressure at which an evaporator operates when fed with liquid by means of capillary expansion device is a function of three modifying characteristics, i. e., the displacement rate of the compressor which is drawing vapor from the evaporator; rate of heat entry to the evaporator, and the amount of liquid in the system. The two evaporators l2 and M are alternately onnected with the same compressor and each evaporator retains its proper refrigerant charge, hence the variable in this case is the rate of heat entry to the respective evaporators. evaporator l4 and is located-in the larger and warmer portion of the refrigerator l3. This causes a more rapid evaporation of refrigerant in Evaporator l2 has a greater surface than the evaporator l2 than in the evaporator l4, hence evaporator l2 operates at a higher pressure than evaporator l4.

Some inventors have recognized the fact that the temperature of a capillary passage affects the rate of refrigerant flow through it and have attempted to utilize this efiect in balancing the operation of two evaporators, but these same inventors have clung to the idea of having a portion of the capillary tube located outside of the cabinet and thermally. associated with the suction tube. While it is desirable to have heat exchange between the warm liquid refrigerant and the cold vapor returning to the compressor, it is not desirable to have any portion of the capillary tube OIIjLaSSage exposed outside of the cabinet or to any high temperature.

Designers usin having encountered the difficulty of running an excessively high head pressure for a period after a start of the compressor, particularly where a portion of the capillary tube is exposed outside of the cabinet. After the system has operated for a short time under this excessive head pressure and the suction tube has become chilled the head pressure drops to normal.

The cause of this high head pressure at the start of a cycle will be understood in consideration of the correct theory of operation'of these so-called capillary devices. Anything which causes vapor to enter -the tube or to form within the tube will restrict the rate of'liquid flow. If the tube is excessively warm any small amount of liquid which enters it and vaporizes causes vapor-lock, which effect has long been recognized in automotive engineering but has not been properly recognized in connection with the operation of capillary tubes and similar expansion devices in refrigerating systems.

The capillary expansion device illustrated in Figs. 1 and 3 is designed to be self-cooling by virtue of the fact that a part of the first liquid to pass through the hole 2| into the interior of core l9 expands and chills the core and its surrounding spirally convoluted tube. noted in Fig. 4 that the liquid line I l is arranged in counter-flow heat-exchange relationship with the suction tube 86. The liquid line it is not a capillary tube of such small diameter that it would of itself restrict the flow of vapor to the extent of causing enough pressure to produce condensation in the condenser w. This tube is preferably somewhat smaller than the usual liquid line of /4 inch outside diameter. For a household refrigerator the inside diameter of this tube ll might be between /16 and inch. While this is not small enough to act as a capillary restrictor it is small enough so that vapor will push liquid ahead of it in the tube instead of the vapor blowing' past the liquid.

The object of this selection of a proper internal I diameter of the tube l I is to insure that any liquid formed in the condenser H1 or in the tube II will 16. On the other hand the inside diameter of the tube should be large enough so that the, velocity of liquid flowthrough it is not too high. This allowed time for heat exchange from the liquid in the tube It to the cold vapor in the tube 86 and avoids the difficulty which has been experienced due to vapor-lock in capillary tubes that are located outside of the refrigerated space. The liquid refrigerant is chilled before it reaches the capillary device and the liquid in the capillary device is further chilled by capillary tubes and other '7 capillary type expanders in refrigerating systems Itwill be evaporation of refrigerant within the core I 9. At the start of operation the tube'86 will not have cooled, .hence the liquid which first enters the expansion device. will be rather warm and it might re-evaporate in the capillary passage and cause vapor-lock if an ordinary capillary tube were used! While I might employ. a tube coiled around the "core i9 instead of employingthe tapered, corrugated tube 20, I prefer the latter for the reason that one thickness of metal provides two spiral capillary passages, one for flow outside of and upwardly around the spiral shell 29' and the other running downwardly between the spiral shell 20 and the core 19. This arrangement provides a further advantage of locating the outlet 2| of the capillary passage at the very beginning of the evaporator and within the capillary device itself without employing awkward return bends of a capillary tube within the evaporatoritself. It will be understood that the chamber within the core l9 actually is. the beginning of the evaporator, both during operation of the freezer and during operation of the warmer box evaporator,

this being the first passage of great enoughcross section to allow the refrigerant to vaporize to a great enough extent to produce an appreciable amount of refrigeration.

The core l9 of the capillary or vapor-lock device is threaded into the body 5 and provided at its lower end with a hexagonal boss so that it can be removed with a socket wrench. .When removed the spirally corrugated tube 20 will slip off toward the smaller end of the part l9 so that the corrugations of the part "are cleanable both inside and out. The corrugations stop short of the lower end of the part 20 so that this'end may be made a tight fiton the tapered outer surface of the part l9 to prevent liquid refrigerant from entering between these two parts from the bots tom. The filter I1 is cylindrical in form and so designed as to be longitudinally compressible.

The filter is thus compressed between the parts I 9 and I6 when the -its gasket.

The spirally corrugated capillary shell 20 is latter is tightened against the filter n due to the fact that it is made to fitfreely over the largest dimension 'of the hexagon end of the part l9, so-that liquid can flow between theflats of the hexagonal boss and the inner wall of the filter. At the smaller end of the part 20! the rolled thread which forms the corrugations is allowed-to run out the end, leavinga passage for the liquid to enter between the parts I9 and 20' after it has passed'through the spiral passage on the outside of part 29. At

.the larger end ofthecone the thread runs into an annular corrugation or bead 24 in the wall of the part 20. The periphery of the bead 24 does not contact the wall of the bore l8, thus permitting the flow of liquid between it and such wall. It will thus be seen that when the filter is disassembled for cleaning it will'be possible to separate the part 20 by pulling it out of the chamber I8 and off of the core i9 so that it may be washed inside and out. When the part 29 is replaced over the member l9 it will not. be necessary .to. register the thread with the hole 2| as the whole may be supported by the part 9 i, which is provided with screw holes for that purpose.

At the outlet end of the evaporator I2 is a small liquid accumulator 13, similar toaccumupurpose of allowing some variation of liquid volume in their respective evaporators. There will be a slight transfer of refrigerant from one evappreferably made from a drawn tube which is rolled to form the thread, thus corrugating the wall in spiral form. The tube is tapered and this taper may or may not be present in the tube prior to the rolling operation. In this rolling operation or in a separate spinning or swaging operation the larger end of the tube is so formed that its inner surface is made an accurate fit upon the conical outer surface of the part. [9 at 30. On the inside of the tube the spiral surface which contacts the part i9 likewisefalls in the same cone. On the outside of the convolutions the surface of bore l8 which contacts the part 29 is a .true cone. It will thus be seen that when the part I9 is screwed into place the spirally cor- I rugated tube 20 will make contact with the part IS in a complete ring at its larger diameter and returning through the. spiral passage between the parts 19- and 20 to the hole 2|. The liquid has acces to substantially the entire surface of 'frigerant than it should have.

orator to the other in both directions, causing aslight fluctuation of liquid volume in each evaprator.

Some refrigerant will be transferred from the warmer evaporator tb the colder one after the compressor has stopped, due to the condenser emptying itself into the freezer evaporator. When the first refrigerant is pumped into the condenser at the start of the run it will come from the box evaporator. There may also be a slight leakage past the push rod 33 and past the valves 62 a'nd 62. These eiTects all tend to transfer refrigerant from the warmer to the colder evaporator. v

An effect operating in a reverse direction is as follows. At the time the compressor stops there will be a pressure within its suction chamber equivalent to the'lowest pressure'ever existing in the colder evaporator. During the idle period there will be vapor flowing. from the freezer past the valve 62' and into the suction chamber of the compressor. Since the sealed unit type of compressor is now the popular one and it is oustomary to have low pressure refrigerant vapor within the housing around the motor and the compressor, it will be seen that this type of motor-compressor unit has a suction chamber which is largeenough to hold a considerable amount of refrigerant in vapor form. 'The amount of re frigerant which. may thus be transferred from the freezer to the box evaporator will exceed the amount of refrigerant that is transferred from the box evaporator to the freezer in the event that the freezer contains slightly more liquid re- On the other hand in the event that the freezer evaporator'is under-charged the amount of refrigerant which 1 the disc valves 62 and 62', though it would be permissible to make the valve 62 and its seat 60 considerably smaller because it is only required to pass liquid at this point. The plug 10 is inserted in the passage 68; preferably with a light drive fit. While the passage 68 and the passage "22 might be made of the same diameter, I prefer to leave a'should'er for location of the plug I by making the passage? slightly smaller.-

The push rod 33. is not attached to either the V valve 40 or the valve 26. It fits very closely in a reamed hole in the body 5. Since the pressure in the passage 18 is the suction pressure of the box evaporator and the pressure within'the bore 23 is part of the time the inlet pressure to the box evaporator and part of the time the inlet pressure to the freezer evaporator, it is apparent that there can -be no great pressure difference between thepassage l8 and the bore 23 to cause leakage around the push rod 33.. There need be no leakage in the direction of reverse fiow past the valves 62 and 62' since the seats 60 and 60 are removable for accurate lapping in production and it has been found that valves of this type will retain their tightness even in compressors and other applications where there is more heat and more pounding of the valve-on its seat. These valves are retained by covers 64 and 64' which are soldered to the body 5. Each of these covers is provided with a downwardly extending point which acts-as a valve stop.

The refrigerator I3 includes a separately insulated compartment I5, which is provided with a door of its own. The door of the larger compartment .of the refrigerator I3 may also enclose the door of the compartment I5 if desired, but in any event we have two refrigerated compartments, each cooled by its own evaporator, and the compartment I5 is cooled to a lower temperature than the other compartment.

The stem of valve 26, which provides a guide in the removable seat member 25, is fluted like the stem 35 of valve 40, on which the flutes 31 are more readily seen.

The functions of the upper stem 4| of the valve 40, the spring 42, the hollow boss 48, the hole 50, and the smaller diameter pin 52 are explained in more detail in the co-pending application above referred to. It is necessary that the pin 52 have considerable clearance either in the hole '50 or in its fit in the stem of the valve 40. This clearance allows the bellows head 46 and the push rod 81 to continue in their downward movement after the valve 40 has been seated, thus allowing the switch 3 to function at its cut out point. As .the bellows is expanded during an idle period by an increase of pressure coming from the freezer this upward. movement of the bellows head 46 weakens the compression on the spring 42 so that less pressure will be required in the passage 18 to open the valve 40. This effect is also explained in the earlier application to which I have referred.

The evaporator 12 is shown diagrammatically at one side of the box I3 in Fig. 4 to allow for showing the control device on a larger scale. It will be understood that the evaporator I2 is to be designed with a surface large enough to do the job of cooling the main food compartment I2 across substantially the entire rear inside wall of the cabinet, located against or adjacent to .the inside of the liner and then hiding the coil by means of a shield. This shield may be considered as a baille to induce air circulation over the coil, or it may be in thermal contact with the coil and thus provide an extended cooling surface for cooling the air within the main food compartment of the refrigerator.

Referring to Fig, 5 we see a modified form of the filter and capillary expander of Fig. 1. This view shows that portion of the body 5 which is modified from Fig. 1. The union I6 corresponds to the union. I6 of Fig. 1. Valvedisc. 62 and its seat 60, the drilled holes 68 and 22 and the plug-I0 serve the same purposes as in Fig. 1, the union II being the connection for the liquid line to the warmer evaporator as in Fig. 1 The drilled hole 66' leads to the lower side of the valve 62 and its seat 60 instead of leading from the upper side as does the drilled hole 66 in Fig. 1. The valve cover 64 is-the same asin Fig. 1 except that it has a slightly longer pointed projection to form the valve stop. Plug 65 is added.

In Fig. 5 the filter and capillarydevice are- I located above the horizontal passages 22 and 68 lary device into the passage 22 at the end of a running period, thus avoiding the slight loss due to evaporation of liquid in the chamber I8 of Fig. 1 and the resulting passage of vapor into the lower temperature evaporator. The closure disc 65 is added to close the opening which must be left for drilling the hole 66'. The bore I0 is in an upwardly projecting boss of the body '5, replacing the bore I0 of Fig. 1. Within this bore is a stack I04 of filter discs and below these is a stack of capillary discs I05, the combined stack of discs being secured by means of the screw I20 and the washer I2I. The discs comprising the filter portion I04 are not shown in detail but will be understood when described as an assembly of discs such as are commonly marketed in the United States by Zenith Carburetor Division of Bendix Aviation 'Corporation and briefly comprise a stack of perforated circular discs and forming the capillary passage are represented by Figs. 6 to 14, inclusive, these figures being numbered in the order that the discs are located from top to the bottom of the stack I05. It will be understood that there may be more than one set of the discs 6 to I3, inclusive, in the stack I05. Each alternative one of these discs is punched with a horse-shoe shaped slot II! to form a passage and the discs above and below it are One punched with holes I I8 to connect a'pair' of the discs which have the horse-shoe-shaped slots.'

Liquid refrigerant after passing through the filter discs passes successively through these horse-shoe-shaped slots which, in combination with the intermediate discs, form a continuous capillary passage from the filter to the lowermost disc, which is so punched as to deliver refrigerant into the passage 22. The entire assembly of filter and capillary discs may be removed for cleaning. Figure 6 represents the disc I06 which may be assumed to be the uppermost one of the capillary stack I 05, going next to the lower disc of the filterstack I04. The stack I05 consists of discs I06, I01, I08,-I09, IIO, III, II2 andII3 in this sequence as shown by Figs. 6 to 13, inclusive, They are placed on the screw [20' in the order given and aligned with each ,other by means of v the tongues I I5, which can best be seenin Fig. 15. While the uppermost disc of the stack maybe number I06, I06, H0 or II2 the lowermost disc will always be H3. The stack may be built up with several sets of discs or a certain number of sets plus apart of a set, but will always start with one of the discs which has the C-shaped slot I I1 andwill always finish at the bottom with the disc 3, which rests upon the larger disc H4. The 'disc I I4 has a notch I I6 cut out of it instead of having a tongue II5, thusi'the tongue 5 of the disc I I3 will extend into the notch of the disc H4 and thereby be held in register with it. Similarly the tongue of the disc II2 will extend into the notch formed by shearing and downwardly bending the tongue 5 of disc '3, continuing thus to the uppermost disc of the capillary stack I05, which disc will be next to the lowermost filter disc of the stack I04. The bottom disc H4 is not only'larger in diameter but preferably thicker than the capillary discs and is punched with the oval hole II9 to pass the screw H2 and to register with the hole II8 of. disc II3 so that liquid refrigerant may flow into the passage 22 from the stack of capillary discs. In this manner the stack I05 of capillary discs may be built up to provide whatever length of passage is required, thus obtaining the desired restriction of refrigerant flow. This restriction need not exactly given, and the discs having holes -I I8 alternate with the discs having the c-shaped slot I", the .production requirements will come out even on the discs I06 to H3, inclusive. This will simplify production of the discs by making it possible to use a gang die, punching out one or more of each disc at each stroke of the press, preferably from a roll or long strip'of brass stock. The press may be equipped with a delivery mechanism which stacks the discs up in the order in which they are to be used, thus facilitating assembly of the stack I05 to the filter stack I04.

, Without changing the die, but merely by substituting stock of a difierent thickness, it is pos- I sible to vary the size of the passage formed by the c-shaped slots 1. Thus if a greater-degree of restriction isdesired it is only necessary to use a thinner sheet of brass or to include more pieces inthe stack I05. The total'height of the stack I05 may be substantially the same for a large number of. thin discs as for a smaller number of thicker discs, yet the two stacks will be adapted for use in refrigerating systems of widely different capacities.

It is not necessary that the filter be of Zenith typ as represented" by the stack of discs I04.

In place of this stack we might use one or more felt washers, as will be seen in Figs. 16 and 17.

Fig. 16 showsa filter and capillary assembly separately from the valve mechanism of Fig. 1, representing an assembly suitable for use in a refrigerating system employing only one evaporator or one having evaporators arranged in series. Liquid refrigerant enters through the union end of the body I30, passing through one 'of the screens I34, through the filter I36,

through the second screen I34 and then through the stack I38 of capillary discs and the end disc 4' into the chamber I40 of the union end I32. The stack I36 comprises discs substantially as shown in Figs. 6 to 13, inclusive, except that the central holes. are not required; the discs being held in place by their outside diameters instead of by a central screw as shown in'Fig. 5. Likewise the disc "4 is the same as the disc II4, except that its outside diameter is the same as that of the balance of the capillary discs. In

match each size of refrigerating system but must fall within a certain rather wide tolerance. The tolerance limit requirements are that the capillary passage must allow free enough fiow so that liquid refrigerant will, under the minimum oper-.

ating pressure difference between high and low sides of the system, pass at the maximum rate of liquid flow that can be obtained with the system on the application for which it is used. The'other limit is that the rate of refrigerant vapor fiow through the capillary stack I05 must be slower than the slowest rate at which vapor is moved by the compressor. The rate of flow in both the case of liquid and the case of vapor is calculated on the basis of pounds weight per unit of-time.

Fig. 15 is shown as a section of Fig. 11 and at double size. This section is mainly to illustrate the tongue II5, which looks the capillary discs together against independent rotation. So far as the tongue H5 is concerned, Fig. 15 may be considered a section of anyof the Figs. 6 to 13, inclusive.

The discs, Figs. 6, 8, 10 and 12, are identical except for the location of the tongue 5- relative 9, 11, and 13, are identical except for the location of the tongue II5 with reference to the hole IIB.

Since the discs are always used in the'sequence 75 up.

assembly,- the screens, the filter material, the

stack I38 and the disc II4" will be inserted in the body of the part I30; The union I32 will now be inserted as shown inFig. 16 and the whole brazed or soldered together. The filter material I36 willpreferably be of a compressible nature, but in any event the amount of filter material and the number of discsin the stack I38 will be so related to the parts I30 and I32 that when the assembly is squeezed together lengthwise to be reversed through the capillary stack I38.

Such an application will be seen in Fig.'9 of my Patent No. 2,145,773, issued January 31, 1939. It

is desirable in this sort of system to have a filter to the G-shaped slot III. Likewise discs, Figs. 7. l

on eachside of the .expansiondevice so that the capillary passages in the stack I38 will be kept free from foreign matter which might clog them The parts I32 in Figs. 16 and 17 are formed with a smaller chamber I40, which allows some expansion or the refrigerant before it passes on to the evaporator. This will produce some cooling eii'ect for the purpose of chilling the capillary stack I80, thus avoiding the vapor-lock difilculty before mentioned.

A further modification of the filter and capillary assembly is seen in Fig. 18. The body I44 is substantially a pipe coupling in which there is a dividing wall I45, having a central opening I46. In the inlet end of the body I44 is a stack I04 of filter discs, secured by means of the screw 1. This screw is located axially of the body I44 by means of the discs I48 on the outlet side of the wall I45. The screw I41 also secures a stack of capillary discs I05, as seen in Figs. 5-to 13, inclusive. Next to the head of screw I" is a heavier disc I50, having a hole I5I located in register with the C-slot III or the hole II8 of the adjacent capillary disc. The locating disc I48 is shown in detail in Fig. 19. This disc is located in the body I44 by means of its outside diameter, very much as is the disc H4 in Fig. 5, but it must also serve to locate the screw I41; hence a central hole is employed instead of the oval hole II9 of Fig. 14. To provide a passage for refrigerant, an additional hole H8 is located in register with one of the holes identified by the same number in the adjacent capillary disc. The disc I48 is also provided with a notch I49 to receive the tongue II5 of the adjacent capillary disc. It will be noted that in Fig. 5 the direction of refrigerant flow is toward the disc 4 or in the direction in which the tongues II5 are bent, whereas in Fig. 18 the direction of refrigerant fiow is away from the disc I48 or in the other direction from that in which the tongues I45 are bent. This makes no difference in the operation of the stack of capillary discs, as will be understood from Fig. 17, in which liquid refrigerant flows part of the time in one direction and part of the time in the reverse direction through the stack I38 of capillary discs.

The filter material of I in Figs. 16 and 17 is preferably such that it may be slightly compressed in assembly and will retain a springy action sufficient to hold the discs of the capillary stack I38 tightly together after long use. In the event that it is not desired to use a material having this characteristic, a separate spring may be provided to insure continued tightness. Such a spring I53 is illustrated in Fig. 18. This spring will not be required when the filter stack I04 is employed, but might in some cases be desirable in the event of substituting fibrous washers such as employed in Figs. 16 and 1'7.

In referring to the discs I06 to H3, inclusive, as forming a capillary passage it should be noted that the restriction is due not only to the capillary action of the passages I" but to the orifice action of the holes I I8. In the event that a modification is illustrated in Fig. 20, wherein the location of the check valve 82 is changed from that shown in Fig; 1. The stop for check value 62 becomes 64 asit has a longer stem like the stop 64' seen in Fig. 1. The change of location of the check valve is to provide for less restriction s of that portion of the liquid refrigerant which flows to the warmer evaporator. This is taken off at the top of the spirally corrugated shell 20,

' means of a special disc located in the stack of.

. axis of I05 in each of the slotted discs. One such the passages III are increased in size and the holes II8 reduced in size the action will be substantially that of a series of orifices. If, on the other hand, the holes II8 are made quite large and the discs in which are formed the passages III are made quite thin the restriction will be mainly due to the small section of the passages 1. It is to be understood that the design may be varied in this manner without departing from the spirit of this invention.

In some cases it may be desired to provide a greater amount of restriction for the flow of liquid refrigerant to the colder-evaporator. Such thus being required to pass through only that portion of the capillary passage which is formed between the part 20 and the wall of chamber I0, whereas that portion of the liquid passing through the hole 22, as in Fig. 1, to the freezer evaporator must also flow through the capillary passage between the parts I0 and 20. The drilled hole 61 of, Fig. 20 provides a passage for liquid refrigerant from the space at the top of part 20 to the check valve 62 and thence to the passage 88. Thedrilled hole 61 is closed by the plug 69. Itwill be obvious that this methodmay also be applied to the type of capillary device illustrated by Figs. 5 to 18, inclusive.

As will be understood from the foregoing description I use the term vapor-lock to designate that type of refrigerant expansion device which operates on the vapor-lock principle. This general term includes both the socalled capillary expansion devices and the orifice type of expansion devices, whether the refrigerant passes through only one fixed orifice or several,

as well as to devices which combine these two methods of refrigerant control, as shown in Figs. 5 to 19 of they accompanying drawings.

Many combinations not shown by the drawings will be obvious from them in connection with this specification. For instance any type of filter might be employed in connection with any of the vapor-lock devices. Also the capillary devices of Figs. 5 to 18, inclusive, might be used in Fig. 1, or in Fig. 20 by providing a separate outlet by refrigerant control discs.

Another variation is to change the order of assembly of discs in the stack I05 so that the liquid reverses its, direction of flow. around the variation is to arrange them in this order: I06- I0'I-I 06--I I3-I06-I0'II05I I3 I05 etc.,

ending with I I3-I I4 01 with I I3-I48. This does not require the parts shown by Figs. 8, 9, 10, 11 and 12. The tongue II5 may, for this arrangement, be formed in part I06 between the ends of the slot III, in part I01 in a position 45 degrees clockwise from hole I I8 and in part I I3 in a position 45 degrees counter-clockwise from hole II8, thus allowing for making the discs smaller in diameter. A similar arrangement is also usable in Fig. 16, ending with H4. In Fig. 17 the same is true, except that the disc I I4 is not used.

What is claimed is: I I

.1. In a refrigerating system, a vapor-lock expansion device comprising a shell helically corrugated to form both male and female threads, a body member externally contacting said threads, and a core member placed within said shell.

2. In a refrigerating system, a pair of evaporators, a pair of valves in mechanically opposed relationship, one of said valves controlling a suction passage leading from one of said evaporators and the other of said valves controlling liquid refrigerant flow to the second of said evaporators, refrigerant flow control means controlling the fiow of refrigerant to said second of said valves,

the connection between said valves being so constructed and arranged that the closing of one valve causes the opening of the other, and meansfor operating'said valves for the purpose of controlling the selective cooling of said evaporators,

one evaporator being designed to operate at a frigerant at a higher rate than it is condensed in said system but not of passing the vaporof said refrigerant at as high a rate as it is compressed in said system.

4. In a refrigerating system, a pair of evaporators connected in parallel, a pair of insulated en-e closures to be cooled by said evaporators, said evaporators and said enclosures being so constructed and arranged that one of said evaporators will operate at a lower suction pressure than the other, a refrigerant flow control device, a liquid supplying connection and a suction connection between each of said evaporators and said control device for supplying liquid refrigerant to and returning refrigerant in vapor form from said evaporators, a check valve in the liquid supplying connection between said control device and the warmer evaporator, a check valve in the suction connection from the outlet side of the colder evaporator, a positively actuated valve in the liquid supplying connection between said control device and the colder evaporator, a positively from the warmer evaporator, and a common actuating means for the last two-mentioned valves.

i 5. In a refrigerating system, a plurality of evaporators designed to operate at different temperatures, valve means enclosed within said system for controlling refrigerant flow to selectively refrigerate said 'evaporators, an expansible member exposed on one side to refrigerant pressure within said system and exposed on its opposite the opposite sides of said compressing means during idle periods thereof, said control means including means causing each of said evaporators to retain some liquid'refrigerant during its idle periods and to start andstop said periods in response to changes of vapor pressure above said retained liquid.

7. In a refrigerating system, a pair. of evapov rators, vapor-lock means for regulating the flow of refrigerant to said evaporators and comprising .16 in either evaporator to stop its operation and to a rise of pressure in either evaporator to start its operation.

8. In a refrigerating system, a pressure imposing element, a condenser, an evaporator, a space, refrigerated by said evaporator, ahigh pressure liquid refrigerant conduit connected with the outlet of said condenser, a low pressure refrigerant vapor conduit connected with the outlet of said evaporator, portions of said two conduits forming a heat exchange section located less than one eighth inch.

10..In a refrigerating system, a condensing actuated valve controlling the outlet of vapor outside of said refrigerated space/and a fixed restrictor connecting the outlet of said high pres sure conduit with the inlet of said evaporator, said high pressure conduit having an inside diameter larger than any diameter that would cause a substantial drop of pressure at the required rate I of flow through it and the upwardly directed portion thereof having an inside diameter smaller than any diameter that would allow vapor and liquid to pass each other therein.

9. Ina refrigerating system, an'evaporator, a space cooled by said evaporator, high pressure liquid refrigerant conduit, a fixed restrictor conmeeting said conduit to said evaporator, a, ,low I pressure refrigerant vapor conduit, and a heat exchange section including portions of said conduits located outside of said cooled space, the inside diameter of that part of said liquid conduit which is in heat exchange with said. vapor conduitjieing greater than one sixteenth inch and unit, an evaporator, a space cooled by said evaporator, a refrigerant flow controlling device of the vapor-lock type connected to supply liquid re-' frigerant to said'evaporator, a high pressure refrigerant conduit connected to supply liquid refrigerant to said flow controlling device, a low pressure refrigerantvapor conduit leading from said evaporator, and a heat exchange section in-,

cluding a portion of each of said conduits insulated from said cooled space, said liquid conduit up to and including the portion in heat exchange with the vapor conduit having an inside size great enough to allow refrigerant to flow therethrough with a negligible drop of pressure,

the sole pressure reducing device for each said tive means being responsive to a drop of pressure said liquid conduit also being small enough to prevent liquid and vapor passing each other therein.

11. In a refrigerating system, anjevaporator, a space cooled by said evaporator, a refrigerant flow controlling device of the vapor-lock type connected to supply liquid refrigerant to said evaporator, a high. pressure refrigerant conduit connected to supply liquid refrigerant to said flow controlling device, a low pressure refrigerant vapor conduit leading from said evaporator, and a heat exchange section including a portion of each of said conduits insulated from said cooled space, said liquid conduit up to and including the portion in heat exchange with the vapor conduit having an inside diameter greater than one sixteenth inch and less than one eighth inch in that portion which is in heat exchange with said vapor conduit.

12. In a refrigerating system, a pair of evaporators operating at different temperatures, a refrigerant flow controllingdevice operable to produce said temperatures and including a liquid control of the vapor-lock type comprising the sole pressure reducing means in said system, said vapor-lock device including means for cooling it in advance of the cooling of said evaporator, a refrigerant conduit conveying. high pressureliquid refrigerant to said now controlling device at each of them, said system a substantially constant pressure throughout its length, a refrigerant vapor conduit leading from said evaporator, and heat exchange means including a portion of each of said conduits.

13. In a refrigerating system, a pair of evaporators, a liquid conduit leading to each of said evaporators, a, suction conduit leading from each of said evaporators, refrigerant fluid flow control means of the vapor-lock type arranged to feed liquid refrigerant to said evaporators one at a time, valve means controlling both the liquid and suction conduits of each of said evaporators, said valve means serving to retain refrigerant in both liquid and vapor phase in each of said evaporators during idle periods. thereof.

14. In a refrigerating system, an expansion device of the vapor-lock type, a pair of evaporators arranged to operate at different times within different temperature limits, each receiving liquid refrigerant through the same rate-of-flowregulating portions'of said expansion device, and valve means for retaining a quantity of liquid refrigerant in the warmer one of said evaporators while it is idle and the colder evaporator is active. I

15. In a refrigerating system, a pressure imposing element, a vapor-lock refrigerant flow control device, a plurality of evaporators connected in parallel in said system and served in common by said device, said vapor-lock device being the only means for reducing pressure upon liquid refrigerant between said pressure imposing element and said evaporators, and valve means between said vapor-lock device and each said evaporator for directing refrigerant flow through said evaporators selectively, liquid refrigerant going to each of said evaporators flowing through the entire length of the same passage of said vapor-lock device.

16. The method of regulating liquid refrigerant flow to first and second evaporators of a refrigerating system one-at a time and causing evaporation of refrigerant to occur within a range of relatively low temperatures in the first evaporators and within a'.range of relatively ,5 higher temperatures in the second evaporator, yyz133955 comprisingihesteps-of imposingwapor-lock fe:

striction on the refrigerant by causing it to flow through a restricted passage of fixed proportions and thereby reducing the pressure on the refrigerant as it enters the first evaporator, then causing refrigerant to change its path of flow to enter the second evaporator and evaporatetherein within the range ,of relatively higher temperatures while continuing to flow through all of the same restricted passage.

17. In a refrigerating system, a pressure imposing element, an evaporator arranged to operate at a low temperature, a second evaporator arranged to operate at a higher temperature, and a refrigerant flow controlling device of the vapor-lock type serving as the sole liquid rate of flow regulating means for refrigerant flowing to either of said evaporators and using its entire flow restricting means for controlling flow to being so constructed refrigerant that substantially no liquid refrigerant is trapped in the high pressure portion of said system at any time and all liquid drains to the low pressure portion of the system in liquid phase during each idle-period.

GLENN MUFFLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,643,179 Sawyer Sept. 20,1927 1,728,183 King Sept. 17, 1929 1,782,689 Hoffman Nov. 25, 1930 1,795,872 Maccaoee Mar. 10, 1931 1,842,529 Maccabee (2) Jan. 26, 1932 1,928,695 King (2) 'Oct. 3, 1933 1,947,929 Emanueli Feb. 29,1934 1,953,433 Replogle Apr. 3, 1934 1,990,663 Mufliy (2) Feb. 12, 1935 2,021,079 Mittendorf Nov. 12, 1935 2,022,771 Killen- Dec. 3, 1935 2,038,153 Williams Apr. 21, 1936 2,038,198 Replogle (2) Apr. 21, 1936 2,042,462 Hahn June 2, 1936 2,045,810 Tweedale June 30, 1936 2,049,413 Cannon Aug. 4, 1936 2,062,857 Askin Dec. 1, 1936 2,063,496 Evers Dec. 8,1936 2,063,745 Kucher I Dec. 8, 1936 2,065,596 Maccabee (3) Dec. 29, 1936 2,071,935 Mufiiy (3) Feb. 23, 1937 2,089,961 Hull Aug. 17, 1937 2,118,290 Black May 24, 1938 2,118,295 Crawford et a1 May 24,1938 4 2,128,020 Smilack Aug. 23, 1938 2,133,948 Buchanan Oct 2571938 2,133,949 Buchanan Oct 25, 1938 1 2,133,950 Buchanan (2) Oct. 25, 1938 2,133,951 Ashbaugh' -1 Oct. 25, 1938 2,133,952 Buchanan (3) Oct. 25, 1938 2,133,953 Buchanan (4) Oct. 25, 1938 Buchanan (5) Oct. 25, 1938 2,133,956 -Buchanan (6) Oct. 25, 1938 2,133,959 Buchanan (7) Oct. 25, 1938 2,133,960 McCloy Oct. 25, 1938 2,133,961 Buchanan (8) Oct. 25, 1938. 2,133,962 Shoemaker Oct. 25, 1938 2,133,963 McCloy (2) Oct. 25, 1938 2,133,968 Van Seiver et al. Oct. 25, 1938 2,133,964. Buchanan (9) .Oct. 25, 1938 2,133,966 Buchanan (10) Oct. 25,1938 2,139,110 Boles Dec. 6,1938 2,141,459 Bronaugh et a1. Dec. 27, 1938 2,145,774 Miiifly Jan. 31,1939 2,165,518 Stoiz July 11, 1939 2,183,343 Alsing Dec. 12, 1939 2,183,346 Buchanan (11) Dec. 12, 1939 FOREIGN PATENTS Number Country Date 218,231 Germany Dec. 24, 1914 184,550

Germany Nov. 2, 1905

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